callID: if callID was given, it is passed through (can identify the response)
url: pass through the url that is being embedded
videoid: contains 11 char long YouTube videoid, if single video embed
playlist: contains playlist id, if playlist embed

Update March 27th 2012: Now oembed-js supports youtu.be urls (YouTube oembed service does not support them). Also now supports videos which have embedding turned off (YouTube oembed does not support these either).